1875] 



WRITINGS OP JOSEPH HENRY. 



463 



distinctly by ascending the side of the cHff to a height of 

 twenty-five or thirty feet. 



All the conditions and results of these experiments are 

 strikingly in conformity with the theory of the refraction of 

 sound which we have previously explained. 



The following recapitulation of the results of the foregoing 

 experiments will exhibit their correspondence with the gen- 

 eral theory : 



Sound heard coining against the wind. 



Experi- 

 ments. 



First 



Third .._. 



Fifth 



Seventh . . 

 Eighth __. 



Average. 



Duration at 

 the top of 

 the tower. 



4.} minutes - 

 12 minutes- 

 12 minutes. 



8 minutes. 



6 minutes. 



42i minutes. 

 8-5 minutes- 



Duration at the base of the 

 cliff. 



^ minute 



5^ minutes 



5^ minutes 



Not heard 



First blast heard, but 

 no other, 

 \ minute after starting. 



12 minutes. 



2-4 minutes 



Difference in favor 

 of audition on the 

 tower. 



4 minutes. 



6J minutes. 



6^ minutes. 



8 minutes. 



5J minutes. 



30i} minutes. 

 6- 1 minutes. 



Sound heard coming with the wind. 



From the first of the foregoing tables it appears that the 

 elevation of the observer has a marked effect on the audition 

 of sound moving against the wind ; while from the second, 

 (with one important exception,) it has very little if any effect 



